Our laboratory played a major role in deriving the laboratory data and in coordinating the cooperative effort that led to the successful uses of single collections of human umbilical cord blood, as an alternative to adult bone marrow, for provision of HLA-matched allogeneic sibling stem/progenitor cells in 3 children with Fanconi anemia. This grant application is a joint effort to evaluate hematologically and immunologically the hypothesis that cord blood cells have a broader basis for use in other disorders currently treated with bone marrow, including adults as well as children. We propose to: 1) measure total hematopoietic stem/progenitor cells in human umbilical cord blood collections by, a) in vitro methodologies with new and currently used growth factors and modified culture conditions to enhance detection of early hematopoietic and more lineage restricted cells, and b) in vivo using immunodeficient (SCID, bg/nu/xid) mice as recipients for human hematopoietic repopulating cells, 2) expand cord blood stem/progenitor cells using various cytokines that can stimulate, enhance, or suppress various stages of their production, as assessed by the above in vitro and in vivo assays, 3) investigate the quantitative and qualitative expression of polymorphic antigens on the progenitors using allo-antibodies to HLA-class I and class II antigens, modulation of these antigens, and susceptibility of progenitors to antigen-specific lysis or growth inhibition by cloned cytotoxic T-lymphocytes against major- and minor-histocompatibility antigens, 4) investigate reactivity of these cells to certain allo-antigens, especially, the cytotoxic T-lymphocyte precursor cell frequency directed against several polymorphic antigens against various related and unrelated individuals, and 5) investigate whether cord blood cells exhibit an antileukemic reactivity against leukemic cells and clonogenic leukemic precursor cells. Adult bone marrow will be comparatively analyzed in the above 5 aims. These studies will provide information on numbers of stem/progenitors in single collections, expansion of such cells in vitro, whether such cells have decreased immunological reactivity allowing them to be used to advantage in situations with reduced graft verses host disease, perhaps in haplo-identical transplants, but with maintenance of antileukemic cell reactivity.